At present, little is known about the cardiovascular changes which take place in the aging individual and the aging hypertensive that dramatically increase the chance of cardiovascular disease and stroke. Research proposed here will investigate the changes which occur in regional blood flow distribution as a function of both age and hypertension and with drug induced cardiovascular stimulation. These data will define changes which may be coincident with the development of age related cardiovascular disease and the role of brain receptor mechanisms in these changes. In other studies the autoregulatory capability of the cerebrovascular system will be examined in aging normotensive (WKY) and spontaneously hypertensive rats (SHR). This information will define the functional capacity of the cerebrovascular system as WKY and SHR age. Other experiments will determine the ability of the cerebrovascular system of aging WKY and SHR to maintain an adequate blood supply, oxygen delivery, tissue oxygen tension and neuronal viability in the face of hypotensive stress. These data will define the cerebrovascular system as a function of age and indicate the reasons for the increased morbidity of aged and hypertensive subjects due to a hypotensive trauma or stroke. A final study will use an electron microscope analysis of the cerebrovascular system of aging SHR and WKY in order to define the histological changes which occur in organelle structure and content which may be coincident with functional changes. The above studies are proposed as an interdesciplinary approach to the analysis of cardiovascular, cerebrovascular and brain functional changes which occur as a functional of age. The results of these experiments are expected to provide needed information on age-related cardiovascular problems as well as providing a base for further experiments on treatments of cerebrovascular disease and stroke.